Why do coffee genetics and varieties matter ?

Because genetics and varieties are key components of cup quality. This has been clearly demonstrated through a major meta-analysis of Cup of Excellence database (RD2 Vision and ACE, 2020). The webinar is available here. Amongst other findings, Gesha and Pacamara varieties were shown to increase SCA scores by 2.1 and 1.0 respectively, all other things being equal.

Because diseases are a threat to coffee. The major threat is the coffee leaf rust (Hemileia vastatrix Berk. and Br.) This disease is so important that it literally shaped the history of coffee growing. To know more, read this excellent book from Stuart McCook “Coffee is not for ever”.

There have been various rust epidemics, but the latest one took place in the Americas the past decade (Avelino et al, 2015. The coffee rust crisis in Colombia and Central America (2008-2013); impacts, plausible causes and proposed solutions). While the causes are multiple, the lack of genetic resistance and/or the breakdown of the genetic resistance of varieties has been pointed. Getting new resistant varieties became an important objective.

There are other important diseases in coffee such as Coffee Berry Disease caused by Colletotrichum kahawae Bridge and Waller. CBD is endemic to East and Central Africa and attacks only C. arabica. Coffee Wilt Disease caused by Fusarium xylarioides (anamorph) Steyaert is a major disease attacking C. canephora (Robusta) in East Africa. It also attacks C. arabica in Ethiopia. 

Several insects have an economic importance on coffee: Coffee Berry Borer (CBB), White Stem Borer (WSB), Coffee Leaf Miner (CLM), Coffee Berry moth…However, genetic or varietal resistance has never been clearly demonstrated for CBB or WSB. Interesting work in Brazil have identified resistance to CLM in different Coffea species and created interspecific varieties using C. racemosa as a parent (see for example Siriema variety here).

Because genetics and varieties will be part of the solution to adapt to climate change and reduction of Carbon Footprint : All scientific studies (see this one for instance) coincide in concluding that climate change will negatively impact the coffee production sector. It is documented in Brazil and in Tanzania through recent papers. While new varieties might not be the silver bullet solution, it will no doubt be part of it. Solutions might be found in current commercial coffee species (C. arabica and C. canephora) but also potentially in new species, such as C. stenophylla.

Most of current analysis on the coffee Carbon Foot Print conclude that fertilization is one of the main components of emissions related to coffee growing. Fertilizers use efficiency is then becoming a Key Performance Indicator of coffee growing. Varieties that efficiently turn fertilizer into production will be contributing to lower the Carbon Foot print. Studies in this area are still scarce but here is a good example of what can be explored.